1. Field of the Invention
The present invention relates to an IC card having a writable memory and more particularly to an IC card for writing a program in this memory by keeping security and a method thereof.
2. Description of the Prior Art
An IC card is excellent in security and finds wide applications. Generally, an IC card has a built-in memory for writing and storing a program as well as various information which can be erased electrically and is used to write various information after a user owns it. For example, the invention disclosed in Japanese Laid-Open Patent Application 6-309558 stores customer information in an IC card and provides quick services. In Japanese Laid-Open Patent Application 6-309384, a use that inspection results and dosing data of a patient in a medical institution are stored in an IC card is described. Furthermore, recently, study has been given to use of an IC card in an electronic money system and an IC card is used to write money information.
As mentioned above, the use method of writing information in an IC card is generally carried out. To keep security, the use method of changing and adding to an internal program stored already and writing a new program is limited.
To improve or change the function of an IC card, there is a case that changing of a program is necessary. Furthermore, to keep security, a case that changing of the cryption method is necessary also may be caused. However, to make it possible to modify an already stored program leads to information opening to public of the microprocessor chip of the IC card and the program thereof and it is not suitable for the use of this IC card for which high security is evaluated.